Wound and injury healing is a complex science affected by many inter-related body functions. Arterial and venous blood flows, lymphatic drainage and body temperature are three of the key factors in the reduction of the time for a wound or injury to heal without complications. Such complications can be life-threatening as well as inhibiting proper wound healing and include edema, seroma, hematoma, and infection, to name a few. Medical professionals address several of these factors with current procedures, but the current art neglects the simultaneous interaction of the previous mentioned blood flows, lymphatic drainage and maintenance of body temperature with wound or injury healing.
Arterial and venous blood flows are intricately related and regulated by the body. Flow pressure ranges are important and remain within certain parameters; changes to them can greatly affect body function as well as wound healing. Arterial pressures normally remain with 120 mm Hg (systolic) and 80 mm Hg (diastolic) and, due to the muscular nature and structure of the body's arterial delivery system, remains relatively constant. On the other hand, venous pressures are more variable because veins are oftentimes compressed and consequently impede blood flow back to the heart. The central venous pressure is normally 0 mm Hg while the venous resistance and the effect of hydrostatic pressure can vary the venous pressure up to 90-100 mm Hg. Key then to the continuous flow of arterial and venous blood flows is the venous pump. The veins are constantly being squeezed and compressed by the body's muscles and other external pressures. It is important to note that the function of the venous system is significantly important to the circulatory filling pressure, an important determinant of cardiac output. The slightest improvement of venous tone and venous filling ultimately will positively affect cardiac output, which can be correlated to as an important factor to improved wound healing. External compression garments have been prescribed as an aid to a reduction in venous flows such as varicose veins and it is a known treatment.
The lymph system is an accessory route used by the body to maintain fluid balance between the interstitial spaces and the blood. Most of the fluid escaping from the capillaries is reabsorbed into the venous capillaries but the remaining 10% is key both to life function and wound healing. The lymph system, with this small amount of fluid, can also carry proteins and particulate matter away from tissue spaces (i.e., a wound site) that would not normally be removed by capillary action. The action of this function of the large vessel lymph system is called the lymphatic pump and is an intricate, fine functioning system of major lymph vessels and valves. Key to this is that the large lymph vessels can be compressed by the walls of the lymphatics themselves or by additional pressures from the surrounding surfaces. This same function in the large vessels occurs in the lymph capillaries. Note that during the normal postoperative period, the patient is restricted from activity, and is sometimes confined to a bed. This quiet period is contraindicated for the lymphatic pump action as there is no additional external factors to increase lymphatic flow during a time that the body most likely has need of such (edema, seroma, hematoma and other complications). An externally applied compression would be helpful and advantageous.
Although mentioned briefly above, the removal of proteins from the interstitial fluid spaces is an important balancing effect. Proteins, in other than proper amounts, can affect tissue colloid osmotic pressures, which can affect capillary fluid absorption and interstitial fluid volumes and pressures. Interstitial fluid pressures are normally negative and are maintained this way by a proper functioning lymphatic pump but even more so by the removal of excess proteins. The area around the postoperative wound site has been most likely traumatized by a number of factors and thus the proper functioning if the wound site has been reduced. External compression can aid the body and more specifically lymphatic flows to maintain protein balances by maintaining the normal "dry" state of the interstitial spaces.
Some common postoperative complications directly relating to interstitial fluid spaces are edema, seroma and hematoma. Many factors can cause the interstitial pressures to increase and without a similar increase in fluid flows, then there is a fluid buildup or edema. A stretch of the tissue spaces occurs with edemas of more than a few days--sometimes even a few hours--so proper and immediate treatment is important. Further to the stretch of the tissue is that fact that this excess fluid disrupts the normal absorption and use of tissue nutrients as the cells are now further from the capillaries. In the case of a wound site, this will slow the recuperative capacities of the body to heal the wound. Seromas can also affect the wound or injury site as does edema but, additionally, the danger of infection is increased. A hematoma similarly affects the wound site. However, it is possible to proactively address the possibility of edemas, seromas, and hematomas by applying external pressure immediately postoperatively with the intent of increasing capillary pressures and lymphatic flows possibly with a target of 17 mm Hg above the normal capillary pressure. This can be done with a properly designed compression garment.
It should be noted that arterial, venous and lymphatic pressures and flows are intricately balanced and interrelated. Additionally, the interstitial fluid volume and pressures are also balanced with these systems. The skin acts as the body's normal enclosure and it has its own elastic characteristics. Injury or wounds may disrupt the normal fluid and pressure balances causing fluids to build up and the skin stretches or contracts depending on the time from injury. Elastic bandaging has been used for many years as an indication in some of these cases, but not widely so as there are well-known cases of the application of conventional elastic bandages or other dressings that due to their design, material composition or application actually worsened the patient condition and caused complications. The correct application of compression is critical and should be able to perform within the intricate requirements of the body's systems. A fabric that could perform as good or better than skin, in stretch, compression, and thermoregulation, would be a great asset to the patient's postoperative regime.
Blood flows are directly affected by the body's autonomic response to maintain the body's core temperature of 37.degree. C. within about 0.6.degree. C. Core body temperature varies depending on external and internal influences, but is much more stable than the body's surface temperature. Heat is produced continually by the body during its metabolic processes and this heat is naturally lost to the surroundings through various mechanisms, principally radiation, conduction, evaporation and air convection. These processes are dynamic and inter-related. The skin is the key organ that is used by the body to maintain temperature and blood flow to the skin's venous plexus and can be up to 30% of cardiac output. Circulation of the skin has two main (and sometimes conflicting functions): 1) nutrition of the skin and 2) conduction of body heat. The rate of blood flow through the skin is the most variable of any other part of the body because the flow to regulate the temperature of the body is affected by the body's momentary metabolic rate and its immediate surroundings. The sympathetic nervous system automatically responds to these internal and environmental factors to vasoconstrict or vasodilate the skin's blood vessels and begin the perspiration process. For example, blood flow to the skin can increase up to 7 times its normal flow if the body needs to cool itself; this is a significant drain on cardiac output requiring blood to be redirected away from other needed body sites (such as a healing wound). Additionally, if the body is cool, then vasoconstriction of the skin occurs and blood flow is redirected to internal core organs and functions (and possibly away from a wound site). There is then a constant conflicting need for blood flow due to the body's need for temperature regulation and tissue nutrition, which can be contrary to the indications for proper wound site healing.
The clothing or in the case of wound sites, the dressings, placed on top of or proximate to the skin directly affect the results of the aforementioned heat-maintaining processes. Their breathability and thermoregulation characteristics influence their effect on the body. Clothing can trap air next to the skin and thus reduce the effect of the convective movement of air against the skin. The radiative effect of the skin is reduced as the clothing can reflect this heat back to the skin reheating it. Finally, perspiration is only effective as a cooling mechanism if it can evaporate; dripping perspiration is lost body energy that could have been directed toward wound healing. First, the clothing must be efficient in wicking moisture away from the skin. In so doing it becomes wet and must be able to maintain body temperature even when wet; many fabrics increase the body's heat loss by 20-30 times when filled with moisture. Clothing that absorbs moisture but does not evaporate effectively in essence reduces the effectiveness of the body's sweating mechanism. Additionally, patient comfort directly affects patient compliance. Since tapes, elastics, and commonly used postoperative and post-injury garments can be noticeably uncomfortable, it is not uncommon for a patient to self-direct the removal of a wound site dressing much earlier than their postoperative instructions to the detriment of their postoperative result. It would be desirable to have an interactive performance fabric that can aid the body in maintaining core body temperature amidst a variety of external environments and keep the skin dry would aid the body in maintaining internal blood flows (to a wound site) for tissue nutrition purposes rather than temperature maintenance.
The wound site is changing over the time of the postoperative period. The wound or injury site postoperative condition is significantly different 24 hours following injury or surgery than it is two or three weeks following surgery. In the cases of some injuries (such as burns), postoperative treatments are often indicated for more than one or two years. Today, patients are treated with singular, stand alone dressings or the medical professional simply modifies standard tapes and elastics to formulate a dressing for the patient's then current condition. No series of specifically designed garments is used although the wound site and the patients' conditions are dynamically changing.
Current garments, bandages, elastics and dressings are constructed of fabrics commercially available. Both the concepts of stretch fabric and elastic garments are nothing new in themselves and are commercially available in many types. Fabrics that absorb moisture are also not new. Most of these stretch fabrics are now manufactured of a spandex material like LYCRA.RTM. (a registered trademark of E. I. DuPont de Nemours & Co.). Spandex is a complex, synthetic, elastomeric material with stretch up to 500-600% and is not practical in solely being used to make garments. It is blended with many other types of fibers such as polyesters, cottons, nylons and others commercially available.
Along with these different fiber blends, different fabric construction methods can be used such as weaving and knitting. Within knitting, tricot and raschel constructions are used. Additionally, there is another type of commonly used fabric that is constructed of similar fibers but manufactured into a web.
All of these in one form or another have limitations and affect the body or more specifically the wound or injury sire in various ways. The use of many blends of fibers in either woven or knitted fabrics is usually limited in that the stretch (elasticity) and the modulus (compressive power or force) are different in the two orientations of the fabric: warp or length direction and the width or fill direction. Ranges vary widely depending on the fibers used, fiber compositions, and manufacturing method but might typically range between 100-180% for the warp and 70-140% for the filler. Modulus readings also vary widely and can range from 2-4 in the warp and 1-3 in the fill. Fiber compositions using synthetics, usually nylons, offer negligible breathability; nylon does not wick or evaporate moisture effectively. Some polyesters do so and it has been a goal of some fabric manufacturers to develop a family of performance fabrics that are used primarily in sport and outdoor activities. There has been a lack of medically-oriented garments to address the combination of the body's ability to recover from wounds or injuries. No medically oriented garments effectively address the combination of the body's need for uniform compression to aid its fluid and pressure systems and the body's need to maintain its temperature. These two key factors directly affect the body's ability to recover from wounds. And, finally, no discussion has been previously made about the possibility that a particular medical garment used immediate postoperative or post-injury might not be applicable 2-3 weeks later. The medical professional knows this reality and oftentimes prescribes different dressings, but in the case of many post-operative and post-injury regimes, they instruct the patient to buy a non-medical item at a retail store which may be impracticable or ineffective.
Additionally, patients have reported discomfort with conventional garments due to excessive heat and moisture buildup between the skin and fabric, especially during summer months in temperate climates and year round in tropical climates. This discomfort can cause the patient to not use the garment for the full physician-prescribed period of time or worse, cause potential medical complications, including improper or prolonged healing, worse scar formation, improper skin retraction, pain caused by fluid buildup or inflammation, and the like.
None of the current art or available resources to today's medical professional encompass the full range of factors influencing the postoperative or post-injury patient. Accordingly, there is a need for a fabric having desirable breathability yet having uniform and high elasticity measurements. The changing of a wound/injury site over time requires changing treatment options. The ambulatory patient has a need to comfortably function in normal activities whole wearing their postoperative/post-injury dressings while complying with their postoperative and/or post-injury instructions. There is a need for dressings, through uniform compression, to assist the body's natural hemodynamic, venous, and lymphatic systems at various stages of wound site or injury healing. There is a need to maintain full percentage of cardiac output directed to natural tissue nutrition at the wound site while minimizing the body's need to regulate its temperature and redirect blood flows. There is a need to, during the above mentioned temperature maintenance autonomic process, improve the body's sweating (cooling) mechanism to more efficiently use body resources (especially blood flow) to cool/heat the body.